Branch Water Pipe Project

This Web page in UNDER Construction!

Description of the Water Distribution System at Coffee Creek Condos

Here is a link to the “As-Built” drawing for the water distribution system and the sewer system dated 30 May 1973.  Below is a portion of that drawing  for just the water distribution system that has been marked to include the condo unit numbers and the location of the “known” branch shutoff valves.

Problem with the Branch Lines

For purpose of identification, the 6-inch (460 feet) and 4-inch diameter (660 feet) cast iron pipe is referred as the main lines. The branch lines are the 1-inch diameter polyethylene pipes coming from the main line to the condos. Typically, these branch lines serve several condos (2 to 4). There have been at least eight failures (split pipe–water leaks) of the branch lines which had to be dug up and and the section replaced. Each failure has required that Spanaway Water Co. shut off the water supply to the entire condo complex to make the repair.  Below is a picture of cross section of the 1” pipe that failed and was replaced:

The reason for failure of the 1-inch branch pipe is that the material excavated from the trench while installing the pipe was used as backfill.  The trench should have been filled with material less than 1/2-inch in diameter in accordance with ASTM D2774 (see pages 32-33 in Polyethylene Piping Systems Field Manual).  Improper fill and compacting causes the pipe to be squeezed by the downward pressure to the point that the pipe splits resulting in a water leak.